Attachment for transits.



N0. 690,0(19. Patented DBO. 3|, IQDL .C. L. BERGER.

ATTACHMENT FOHTRANSITS.

(Application filed. Feb. 19, 1901.)

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' IE1) STATES PATENT OFFICE.

CHRISTIAN L. BERGER, OF BOSTON, MASSACHUSETTS.

ATTACHMENT FOR TRANSITS.

SPECIFICATION forming part of Letters Patent No. 690,009, dated December 31, 1901.

Application filed February 19, 1901. Serial No. 47,989. (No model.)

To ctZZ whom, it may concern:

Be it known that I, CHRISTIAN L. BERGER, a citizen of the United States, residing at Boston, county of Suffolk, State of Massachusetts, have invented an Improvement in Attachments for Transits, of which the following description, in connection With the accompanying drawings, is a specification, like letters on the drawings representing like parts.

My present invention is an attachment for field instruments, especially for transits, whereby the graduated circle or are may rotate with the telescope or remain stationary during the movement of the latter, as maybe desired, according to the purposes of the operator.

In many situations, especially in mine-surveying, it happens that it becomes necessary or advisable to use the telescope without the vertical circle, or in some instancesas, for example, where the place is extremely confined and there is not room to swing the graduated arc toward or from the operator, as the case may be-it is desirable to change the po sition of the are relatively to the telescope, so that it can be moved in some other direction and read from the difierent standpoint. Accordingly I have devised a simple means applied to engineering and surveying transits for accomplishing these objects.

The details of construction of my invention and the further advantages thereof will be pointed out in the course of the following description, reference being bad to the accompanying drawings, in which I have shown certain embodiments of my invention.

In the drawings, Figure 1 is a fragmentary detail, in side elevation, showing the usual instrument with my attachment applied thereto. Fig. 2 is a central vertical section thereof. Fig. 3 is a similar sectional view of the modified construction. Fig. 4 is'a rear elevation of the clamp portion of the attachment.

As will be readily understood by those skilled in the art, it is essential, and particu larly so in mine-surveying, that the graduated limb of the instrument should be in an absolutely true circle, as otherwise the graduations thereon being at different radial distances from the center will not correspond to the same angles and, moreover, will not read correctly with relation to the Vernier.

My present invention relates particularly to means whereby in a movable-arc type of instrument the arc itself or graduated limb cannot vary from its original shape as it is clamped and unclamped from the axis of the instrument.

For purposes of illustration my improvement is shown in connection with a telescope a, mounted in an axis a, journaled at a in standards a a Vernier, (indicated at at) and usual adjusting device a a, cooperating with a bracket a A graduated limb or quadrant is shown at b, and as heretofore constructed this limb would be secured to the aXis of the telescope by having its hub split and clamped in place, thereby tending continually to render the instrument unreliable, because of the liability of the arc to spring one way or the other out of a true circle.

According to my present invention I make the hub 1) solid, providing the same with a shoulder or flange b at one side, on which is mounted the adj usting-arm a which carries the adjustment a a, and on the opposite side of the hub b I secure by any means, as a screw 12 an independent clamping-ring Z1, shown as split at b and provided with one or more sawcuts b for giving the proper resiliency, the split ends at b being provided with a clamping thumb-screw b by which they may be permitted to separate or may be drawn together for the purpose of clamping the same rigidly on the spindle ct. The shoulder 79 of the hub 12 may project beyond the arm a as indicated at N, Fig. 3, and is provided with coarse threads, on which is mounted a similarly-threaded clam ping-plate 17 which works between the adjacent face of the arm a and a rotating nut Z1 the latter serving to hold the parts snugly in place and limit the movement of the clamping-plate I)"; or, preferably, instead of this construction the depending portion of the arm a is provided with a crossbar a ,in which is mounted a setbolt a of any convenient type, (see Figs. 1 and 2,) adapted to engage a socket b in the graduated limb for clamping the arm a and limb I) together when desired.

In operation when for any reason it is necessary to preventthe graduated limb from moving with the telescope the thumb-screw b is loosened, thereby disengaging the graduated limb from rigid connection with the spindle-axis, and the arm a is rigidly clamped to the graduated limb by the engagement of the set-screw a therewith or by swinging the clamping-plate 6 over toward the right into clamping position. 'Ihereupon the operator may freely use the telescope without incommoding himself by having the graduated limb turn therewith. On the other hand, when it is desirable to have the graduated limb move with the telescope the clamping devices 19 or a are released and the thumb-screw b is tightened,whereupon the graduated limb will move with the telescope, and its readings may be taken in usual manner with relation to the Vernier a.

It will be evident from the foregoing description that there is no possibility of variation in the curvature of the graduated limb I), because its hub is solid, and it is secured in place by anindependentclamping-ring,wliich is preferably secured thereto by one screw only, so that whenever movement takes place the clamping-ring is entirely without influence on theshape of the graduated limb,while at the same time the graduated limb when released from movement with the telescope is readily held against accidental turning movement by either a clamping device 11 or a as the case may be.

I do not limit myself to the specific details of construction herein set forth or otherwisethan is defined in the claims.

Having described my invention, what I claim as new, and desire to secure by Letters Patent, is

1. In a surveying instrument having a telescope, a graduated limb containing means for mounting on the axis of said telescope, and a clamp independent of said mounting means, said clamp being connected to the limb and including operating vmeans cooperating with the rest of the clamp and connection for clamping the limb on or releasing it from said axis, without liability of varying the shape of the limb or any part thereof.

2. In a surveying instrument having a telescope, a graduated limb, said limb having an integral hub mounted on and fitting around the axis of said telescope, a clamping-ring secured to said hub and capable of contracting and expanding movement without affecting said hub, and means for clamping said clamping-ring.

3. In a surveying instrument having a telescope, a graduated limb, said limb having an integral hub mounted on and fitting around the axis of said telescope, a clamping-ring secured to said hub and capable of contracting and expanding movement without affecting said hub, means for clamping said clampingring, said limb having a socket, an arm mounted adjacent said limb,and a set-screw threaded in said arm in position to engage said socket for holding the limb against movement with the telescope.

4. In a surveying instrument having a telescope, a graduated limb, said limb having an integral hub mounted on the axis of said tele scope, a clamping-ring secured to said hub and capable of contracting and expanding movement without affecting said hub, means for clamping said clamping-ring, said limb having a socket, an arm mounted adjacent said limb, a set-screw threaded in said arm in position to engage said socket for holding the limb against movement with the telescope, and a rotating nut mounted on said axis for clamping the hub of said limb and said arm in place. 5. In a surveying instrument, a telescope, an axis therefor, supports in which said axis is mounted, a graduated limb mounted on said axis, a clamp for clamping or releasing said limb from movement with said axis, an arm mounted on said axis, means for securing said arm rigidly to said support, and a clamp for clamping said arm and said movable limb rigidly together, when desired.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

CHRISTIAN L. BERGER. 

